| 摘要 |
PURPOSE:To eliminate the influence of impulse noise by providing an input amplitude monitoring circuit which gives a PCM signal to a sampled value storage circuit, which is judged to be smaller than a previously decided amplitude value. CONSTITUTION:The input amplitude monitoring circuit 5 compares the amplitude value of the inputted PCM signal with a judgement threshold which is a little larger than the max. value of the amplitude value being judged to be a silence part and outputs judgement result which shows that the inputted PCM signal is smaller or larger than the judgement threshold to the sampled value storage circuit 2. The sampled value storage circuit 2 successively stores the PCM signal which is judged to be smaller than the amplitude value being previously decided by the input amplitude value monitoring circuit 5 for only a section where a power value is calculated. A power value calculating circuit 3 respectively squares the sampled values in the section, obtains a sum so as to calculate the power value and outputs it to a holding circuit 4. The holding circuit 4 outputs the output value of the power value calculating circuit 3 to an output terminal 7 when the detection output of a sound and silence detecting equipment 6 is silence and outputs the power value at the time of immediately preceding silence to the output terminal 7 when the equipment 6 has sound. |
